Transformer



June 16, 1925.

W. L. CASPER TRANSFORIEH Filed Oct. 19. 1922 lnvenfor:

William L. Cas er,

Patented June 16, 1925.

UNITED STATES p 1,542,372 PATENT orrlce.

WILLIAM L. CASPER, OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y-, A CORPORATION OF NEW YORK.

TRANSFORMER.

Application filed October 19, 1922. Serial No. 595,538

To all whom it may concern:

Be it known that I, WILLIAM L. CASPER, a citizen of the United States, residing at Brooklyn, in the county of Kings, State of New York, have invented certain new and useful Improvements in Transformers, of which the following is a full, clear, concise, and exact description.

This invention relates to transformers and particularly to balanced transformer circuits.

An object of this invention is to provide means for eliminating unbalanced capacity effects in a transformer. Another object of this invention is to provide a transformer which may be introduced into a signaling circuit without disturbing the balanced relation of the two sides of the si aling circuit with respect to ground.

n accordance with the form of this invention hereinafter described in detail, the unbalanced capacity effects between the various parts of a transformer are eliminated by surrounding the core of the transformer 7 with a split shield, each half of the shield being electrically connected to one wire of a twlsted pair which forms the transformer winding adjacent the core. This arrangement serves to remove unbalanced electrostatic capacit 1 effects which would otherwise destroy t e symmetrical distribution of the capacities of the various windings of the transformer with respect to the line wires of the signaling circuit and ground; This type of transformer is particularly useful in phantom circuits where a high degree of balance is necessary.

The drawing illustrates this invention embodied in an auto-transformer which may be employed for interconnecting signaling or telephone lines of different impedances.

Fig. 1 shows diagrammatically the method of connecting the various coils. Fig. 2 is'a diagrammatic plan view of the transformer.

Referring to the drawing in which the same reference numerals are used in both figures, 8 represents a transformer core of any desired construction, which may be toroidal for example. Surrounding the core 8 is a split metallic shield, the two halves 9 and 10 being insulated from each other and from the core; Windings 11 and 12 represent wires which' may be wound in a plurality of layers around the shield 9 and 10 as a twisted'pair. While the windings 11 and 12 as well as the other windings are multilayer windings they are shown in Fig. 2 as single layer windings, so as to avoid confusion. Windings 13 and 14 are superposed upon the twisted pair 11 and 12, windlng 13 being wound on one half of the core and winding 14 on'the other half. Windings 15 and 16 are then wound on the core, winding 15 being superposed on winding 14 and winding 16 being superposed on wmding 13. Conductors 17 and 18 represent a section of a signaling circuit connected tothe outer terminals of windings 15 and 16, while conductors 19 and 20 represent a second sec tion of a signaling circuit connected to intermediate points of the auto-transformer. The letters i' and 0 have been applied to various parts of the transformer windings to indicate which part is the inner layer of the winding or the outer layer of the winding, the letter 1 representing the inner layers and the letter 0 representing the outer layers. Windings 14 and 16 are wound inopposite directions from windings 15, 13,11, and 12. Windings 15,13,117, 12,11 and 16 are connected in series aiding to :1 current passin from line 17 to line 18 through these impedances in the order named.

The various capacities shown in the drawing in dotted lines represent the natural capacity efi'ects existing between adjacent windings, between the windings and the transformer casing 22 and between thewindings and the split shield 9, 10.

Capacity 23, which represents the natural capacity between the outer layer of winding 15 and casing 22, is symmetrically situated in the circuit with the capacity 24 between the casing and the outer layer of Winding 16, so that these two capacities do not unbalance the transformer with respect to the two sides of the signaling circuit,

which are required to be maintained at equal potentials above ground. The following capacities are symmetrically located with re spect to the two sides of the signaling circuit and consequently do not tend to unbal' ance the transformer; capacity 25 between the outer'layer of winding 14 and the inner layer of winding 15; capacity 26 between the outer layer of winding 13 and the inner layer of windinglfi; capacity 27 between the outer layer of winding 11 and the inner layer of winding'14. Capacity 28, between the outer layer of winding 12 and the inner windiue' ietu en the or inner layer 7 two capacities are e'ti cotii'ei i' c nnected n hunt re pect]\el t w it and l2. Capacity 4:0 is uus inune i'i short circuited. Capacity outer layers oi the twisted pair ll and lil, is eileetirely balanced by rapacit 'll between the inner la 'e ot the twisted pair. ween the two wires ot the ,lnere in capacity the t pair length. For cierern onl at the ends b u e i a it is evident that toic this m llIY located on H -I, i point oi the windin there is one e iuit element n the other s e F '\'nunetricall5 placed. Caacit; 32 between l f or ot wind- 1 sale oi the ueuti'a in l and the Si eld f shunted around winding; ll bv Trig; wire 33.

r la e I 0 connected tie it inns a and the u the col 4 .,d that they counter balance each other r are symmetrically located with re ct to ih two sides of line 1 i inc or are short-circiuted. J transformer is, theretor o particular liliportance in sigraling c .::u ts such as teleph ne circuits. since its introductioninto the circuit will not disturb the balance of the sig ualinn' line. Th i portauce of maintaining the two wires of a si ual line balanced with re pect to ground; possible croi all; e "ects which may take place be ween the g ven circuit and neighbor e; circuits whenever any capacity unbalance ts and more particularl i when that circuit is used as a side circuit to the lie cross-tal cll'ects between the plumtom circuit and the side circuit.

In the above described transformer arm inaing's 11 and 12, which form ll, of course, he composed The resulting if i is due to the of an equal number of' turns. To order o obtain an exact balancing of the czl])aoil' elects, winding 1?) should be composed of the same number of t-urnsas winding 14 and winding 1:") should be composed of the same number of turns as winding ill. It will also be found advisable to balance the d. c. resist-- ances of the series of the windings.

Ito's to bounderstood that various modifications of the above-described transformer arran einentmaybe made without departing in any-wise from the spirit of this in mntion asdetincd in the appended claims This invention, for example is not limited in its utility to auto-transforn'iers, butma be applied to'other types of inductance eleineula or other electrical devices composed oi a plurality oi. windings arranged on a common core.

This invention claimed is:

l. A. transtorn'ier comprising a core, a winding on said core wound in a plurality of layers,- said transformer" having a natural capacity between a layer of said winding and another part of said transformer, which capacity is unsymmetrically located with respect to theiexternal terminals of said transtormer,- and means comprising a shield surrounding a, portion of said core for symniei rically locating said capacity-with HSPQCt to said external terminals.

.9. transformer comprising a core. a

iflll flillgfill said core wound in a pllil' lllld ot layers, sai(ltrar1st'mmei"havi11g a natural capaeitybetween a layer of saidwinding and said core, and meanstor short-circaitingsaid capacity transfonner having a core. a shield insulated sections, a winding surrounding said shield. and rmmeetions trom different-points on said whaling to dittemnt sections ot'sa'id shield.

-'l. An inductance device comprising a shield of a plurality ofiinsulated sections. a winding surrounding said shield, and a cnnnect-iou from each of a plurality of said sections to said'winding.

e 5. A transfonner comprising a core, a shield surrounding said core of a plurality of insulatedse'ctions, a winding of a plurality of layersiaround said shield, said transfon merhnving a natural capacity between said shield and theadjacent layer of said winding, and a connection between another layer of said winding and said shield 6. An inductance device comprising a orea shield surrounding said core. a winding' around said shield; and a connection between said shieldandsaid winding to symmetrically connect: with respectto the external terminals ofsuid devicethe natural capacity shield and 'the inner layer of of windin s each comprising a plurality of layers am having a common terminal, a ma netic core, a shield between said core and saic windings, and a connection from said shield to the outer layer of one winding to short-circuit the capacity between said shield and the inner layer of said other winding.

8. A transformer comprising a core, a plurality of windings around said core, a casing surrounding said windings, and means comprising an electrostatic shield surrounding said core and comprising a plurality of insulated sections for causing said transformer to be elec-trostatically balanced.

9. A transformer comprising a core, a shield with a plurality of sections around said core, a twisted pair of wires wound in a plurality of layers surrounding saidshield, and a direct connection from the outer layer of each of said wires to a portion of said shield.

10. A transformer comprising a core, a plurality of windings surrounding said core,

and means for preventing an electrostatic un balance between said core and said windings.

11. A transformer comprising a metalii casing and an electrostatically balanced windingcomprising four multi-layer sections, two of which sections are wound on one portion of the" core and the other two on another portion of the core said sections being serially connected in the following order: the inner layer of the outer section on one part of said core to the outer layer of the inner section on the other part of said core, the inner layer of said last mentioned section to the inner layer of the other inner sec tion and the outer layer of said last mentioned inner section to the inner layer of the other outer section, said two last mentioned sections being wound in the opposite direction to said two first mentioned sections.

In witness whereof, I hereunto subscribe my name this 17th day ofOctober A. D.,

WILLIAM r L. CASPER. 

